1. Field of the Invention
This invention relates generally to lens covers for operating microscopes and, more specifically, to an objective lens cover employed in conjunction with disposable sterile operating microscope drapes.
Operating microscopes are employed in the performance of various surgical procedures. As in any surgical procedure, it is necessary to maintain the operative site in as sterile a condition as possible. Because the microscope used in microsurgery is placed in close proximity to the operative site, the microscope itself is usually draped with a transparent or opaque surgical drape to prevent stray materials, such as dust, from falling from the microscope into the operative field. Since the objective lens of the microscope is placed in close proximity to the operative site, it is necessary to protect the objective lens of the microscope from being smeared with body fluids from the patient or with various solutions which may be used in surgery. In addition, the objective lens covers are used to protect the objective lens of the microscope from the danger of being contacted with a surgical instrument and scratched or otherwise damaged.
Operating room microscope drapes are generally fabricated from plastic materials to completely encase the operating room microscope as well as the structure that is used to support the microscope during the surgical procedure. Prior art microscopes drapes have included objective lens cover assemblies of various configurations, but these prior configurations have not been totally satisfactory. U.S. Pat. No. 3,528,720 to Treace discloses a microscope drape made of a clear plastic envelope which can be fitted over an operating microscope. The drape includes a circular aperture positioned to receive the objective lens of the microscope and an objective lens ring to frictionally fit the objective lens frame on the microscope. The ring is fabricated from a resilient deformable plastic material and is fitted onto the objective lens frame. The structure disclosed in this patent does not include a lens cover but protects the lens from contact by surgical instruments by providing a ring structure 53 which projects downwardly from the point of attachment of the lens ring to the microscope.
U.S. Pat. No. 3,796,477 to Geraci discloses a flexible lens housing which employs a removable lens cover. The lens cover disclosed in Geraci is force-fitted into a notch or groove in the interior of the lens housing. In order to remove the lens cover in the Geraci drape for replacement, it is necessary to deform the lens ring housing or ring and possibly remove the lens ring housing from the microscope. The removal of the lens ring housing from the microscope is not desirable, as particles on the interior portion of the drape might be dislodged during the removal of the lens ring housing and fall into the operative site. In order to replace the lens cover in the Geraci drape, it is necessary to fit a new lens cover into the groove within the lens housing, which is a difficult manipulative procedure considering that it is important not to come into contact or smudge the lens cover, which would possibly distort the image as seen through the lens of the microscope.
The Geraci U.S. Pat. No. 4,266,663 also discloses an operating microscope with a lens cover which, again, is snapfitted into a lens housing and may also be difficult to replace since it must be grasped by the tabs on the lens cover without contacting the central surface of the lens cover.
U.S. Pat. No. 3,698,791 to Walchle et al. also discloses a microscope drape with an integral lens cover secured in the drape. The lens housing in the Walchle et al. reference frictionally engages the objective lens through an aperture in the drape. The housing is made of a cross-linked polyethylene foam which is secured to the drape with a pressure sensitive adhesive. The lens cover in the drape of Walchle et al. is not replaceable, and, if the cover is smeared, it would be necessary to change the entire drape.
The lens cover of the present invention overcomes the problems with the prior art lens covers and also provides a lens cover which may be used with an illuminating microscope. In an illuminating microscope, there is a source of light, either through a fiberoptic device or through a direct light source, which is positioned in proximity to the objective lens. The surgical drapes in the above-mentioned references are not capable of providing access of this light source through a lens cover, and these drapes may not be used with microscopes with illuminating sources adjacent the objective lenses.